The present invention relates to an electromagnetically operated valve assembly for selectively opening and closing an intake or exhaust port of an internal combustion engine under electromagnetic forces.
Intake and exhaust valves for selectively opening and closing the intake and exhaust ports of an internal combustion engine are generally operated by a valve operating mechanism which is actuated by cams on a camshaft.
Electromagnetic valve control systems for controlling the timing of operation of the intake and exhaust valves of internal combustion engines through an electromagnetic actuator means are disclosed in Japanese Laid-Open Patent Publication Nos. 58(1983)-183805 and 61(1986)-76713. These prior electromagnetic valve control systems are however not addressed to an improvement in intake and exhaust valves. The intake and exhaust valves used in the known electromagnetic valve control systems are problematic in that since the valves are made of metal, they are heavy, poor in response, and require large driving forces.
A valve made of a ceramic material is light and suitable to perform required valve functions. However, the ceramic material presents a large magnetic reluctance as it is nonmagnetic. Accordingly, the electromagnetic actuator means for use with the ceramic valve is required to have an increased magnetic path cross-sectional area. As a result, the movable member of the electromagnetic actuator means is heavy, and the same problems as those of the above conventional valves still remain to be solved.